Vacationing in France? Watch Out for Deadly Seaweed

Vacationers, beware! A potentially dangerous seaweed could be a threat to the health of millions of beachgoers on the shores of Brittany, western France.

Ulva Lactuca – more commonly known as sea lettuce – is harmless while living in the water. But it can become fatal when it decays on land after being washed ashore.

A gas which formed under a crust of seaweed killed a horse at the end of last month on a beach in Saint-Michel-en-Grève, on the Côtes d'Armor, the only one of the four departments of Brittany affected by the phenomenon. The horse collapsed and died after inhaling the deadly hydrogen sulphide gas. The horse rider lost consciousness and was treated at a local hospital. Last year, two dogs died in the same area in the same conditions.

This "green tide" has been present on Brittany beaches for the past 30 years. Environmental groups have blamed the use of huge amounts of nitrates used in intensive farming for a build-up of the seaweed. The nitrates seep into the region's rivers and end up in the sea.

Despite its small population of 3 million people living on just 5 percent of the country's agricultural land, Brittany is home to 60 percent of France's pig farms, 45 percent of its poultry farms and 30 percent of its dairy farms.

"The green seaweed is the physical expression of the pollution of the water in Brittany by nitrates. The population of Brittany is waiting for the reduction of at least 1/3 of the pollution by the nitrates of the water," Jean-Francois Piquot of the environmental group Eau et Rivieres de Bretagne told ABCNews.com.

"If the green seaweed had not rotten the Côtes d'Armor [sic], there would have been much more people here over the years," he added.

"Oh no, we don't let the children wander around, with everything that has happened, there were two dogs which died on this beach, a horse more recently, so if the seaweeds are capable of killing a horse, then…" a mother on a beach told the television channel, France 2 TV today. "When people see all these seaweeds, they leave," another woman added.

This potentially lethal fumes from the rotting seaweed have worried local residents and threatened the lucrative tourist industry.

"Tourists are not taking any risks by going on beaches which are accessible to the public," the Brittany Tourist Board recently said in a statement. "The recent incident involving the death of a horse must be treated very seriously but remains nevertheless very rare."

The board also said that, "As the green seaweed poses no risk to swimmers, swimming has not been restricted in these areas," adding that Brittany has a 2700 km coastline (about 1650 miles) and "only 200 meters (or about 650 feet) has been closed recently due to the green seaweed."

An estimated 9 million tourists visit annually Brittany, close to 30,000 of whom from the U.S., according to the Brittany Tourist Board.

"There are green seaweeds in Brittany, but there are no public health risks," said Piquot. "Tourists must continue to come to Brittany."

According to Eau and Rivieres de Bretagne, local towns have spent $1.42 billion over the past 30 years to collect, stock and eliminate the seaweed. But the seaweed continued to invade Brittany beaches over the years and fed up with the failure of the French government to find solutions to this problem, 400 local residents organized a demonstration on a beach a few weeks ago.

And the protestors may have been heard.

On Thursday, French Prime Minister Francois Fillon cut short his vacation and announced in Saint-Michel-en-Grève, where the horse died, that the government would take care of the cleaning up of Brittany beaches invaded by the seaweed. "These pollutions present a danger for the health. A study has showed the toxicity of these green seaweed in a certain concentration," Fillon told reporters.

This study ordered by the Ministry of Ecology indeed revealed yesterday that the gas coming from seaweed in decay "can be deadly" in case of a particularly important concentration. "Measures carried out on the Saint-Michel-en-Grève site … have showed here and there that gas coming from sediments containing notably seaweed in decay could be dangerous," the report from the National Institute for Environmental protection and Industrial Risks Management said. The report stresses that hydrogen sulphide is toxic by inhalation. It reveals that, at 1,000 ppm (parts per million), a value which was found in some parts of the beach where the horse died, "it can be deadly in a few minutes."

Prime Minister Fillon also said that a government mission would be put together within the next three months "a plan of action to fight against the proliferation of green seaweed and propose efficient collecting solutions and protection of the population."

"We're going to experiment the collection of seaweed at the end of winter, at sea, in order, we hope, to avoid the proliferations like the one we've encountered this summer."

"We have made extremely precise commitments with farmers concerning the significant reduction of farm inputs. These objectives will be held," he added.

But environmentalist Piquot brushed off Fillon's remarks, saying, "It's been 25 years that I hear that measures are going to be taken and it's been 25 years the situation has not improved. Frankly, I'm not particularly optimistic."